(a) Field of the Invention
The present invention relates to a electron emission device, and in particular, to a electron emission device which forms a resistance layer on an electron emission source to uniformly control the electron emission at respective pixels
(b) Description of Related Art
Generally, the electron emission devices are classified into a first type where a hot cathode is used as an electron emission source, and a second type where a cold cathode is used as the electron emission source. Among the second typed electron emission devices there are field emitter array (FEA) types, surface conduction emitter (SCE) types, metal-insulator-metal (MIM) types, metal-insulator-semiconductor (MIS) types and ballistic electron surface emitting (BSE) types.
The electron emission devices are differentiated in their specific structure depending upon the types thereof, but basically have an electron emission unit placed within a vacuum vessel, and a light emission unit facing the electron emission unit in the vacuum vessel.
Generally, the FEA typed electron emission device has a front substrate and a rear substrate. Emitters are formed on the rear substrate as electron emission sources, together with cathode electrodes and gate electrodes for emitting electrons from the emitters. Phosphor layers are formed on the surface of the front substrate facing the rear substrate, together with an anode electrode receiving high voltages for accelerating the electron beams.
The FEA typed electron emission device commonly has a triode structure with three electrodes. As shown in FIG. 11, gate electrodes 3 are formed on rear substrate 1, and insulating layer 5 is formed on gate electrodes 3. Cathode electrodes 7 are formed on insulating layer 5 while crossing gate electrodes 3. Emitters 9 are formed at the one-sided periphery of cathode electrodes 7 per the respective pixel regions where gate electrodes 3 and cathode electrodes 7 cross each other.
Anode electrode 13 and phosphor layers 15 are formed on the one-sided surface of front substrate 17 facing rear substrate 1, and grid electrode 11 and support 30 are provided between rear substrate 1 and front substrate 17 to focus the electrons emitted from emitters 9.
When driving voltages are applied to cathode electrode 7 and gate electrode 3, a strong electric field due to the voltage difference between the two electrodes is applied to emitter 9, and electrons are emitted from emitter 9. When a positive (+) voltage of several hundreds to several thousands volts is applied to anode electrode 13, the electrons accelerated toward front substrate 17 collide against phosphor layers 15 to emit light.
With the above-structured electron emission device, when the electron emission of emitter 9 is uniformly controlled per the respective pixels, desired grays can be correctly expressed with heightened screen color purity, and the inter-pixel brightness characteristic can be maintained constantly.
However, with the usual FEA typed electron emission device, the shapes of emitters 9 at the respective pixels can be made non-uniformly due to processing differences, and this can result in differences in the electron emission per respective pixels. Furthermore, the electron emission at the pixels where the voltage drop is made due to the internal resistance of cathode electrode 7 and gate electrode 3 may become deteriorated, resulting in uneven electron emission at the respective pixels.